This invention relates generally to the field of phacoemulsification and more particularly to torsional phacoemulsification cutting tips.
The human eye in its simplest terms functions to provide vision by transmitting light through a clear outer portion called the cornea, and focusing the image by way of the lens onto the retina. The quality of the focused image depends on many factors including the size and shape of the eye, and the transparency of the cornea and lens.
When age or disease causes the lens to become less transparent, vision deteriorates because of the diminished light which can be transmitted to the retina. This deficiency in the lens of the eye is medically known as a cataract. An accepted treatment for this condition is surgical removal of the lens and replacement of the lens function by an IOL.
In the United States, the majority of cataractous lenses are removed by a surgical technique called phacoemulsification. During this procedure, a thin phacoemulsification cutting tip is inserted into the diseased lens and vibrated ultrasonically. The vibrating cutting tip liquefies or emulsifies the lens so that the lens may be aspirated out of the eye. The diseased lens, once removed, is replaced by an artificial lens.
A typical ultrasonic surgical device suitable for ophthalmic procedures consists of an ultrasonically driven handpiece, an attached cutting tip, and irrigating sleeve and an electronic control console. The handpiece assembly is attached to the control console by an electric cable and flexible tubings. Through the electric cable, the console varies the power level transmitted by the handpiece to the attached cutting tip and the flexible tubings supply irrigation fluid to and draw aspiration fluid from the eye through the handpiece assembly.
The operative part of the handpiece is a centrally located, hollow resonating bar or horn directly attached to a set of piezoelectric crystals. The crystals supply the required ultrasonic vibration needed to drive both the horn and the attached cutting tip during phacoemulsification and are controlled by the console. The crystal/horn assembly is suspended within the hollow body or shell of the handpiece by flexible mountings. The handpiece body terminates in a reduced diameter portion or nosecone at the body's distal end. The nosecone is externally threaded to accept the irrigation sleeve. Likewise, the horn bore is internally threaded at its distal end to receive the external threads of the cutting tip. The irrigation sleeve also has an internally threaded bore that is screwed onto the external threads of the nosecone. The cutting tip is adjusted so that the tip projects only a predetermined amount past the open end of the irrigating sleeve. Ultrasonic handpieces and cutting tips are more fully described in U.S. Pat. Nos. 3,589,363; 4,223,676; 4,246,902; 4,493,694; 4,515,583; 4,589,415; 4,609,368; 4,869,715; 4,922,902; 4,989,583; 5,154,694 and 5,359,996, the entire contents of which are incorporated herein by reference.
In use, the ends of the cutting tip and irrigating sleeve are inserted into a small incision of predetermined width in the cornea, sclera, or other location. The cutting tip is ultrasonically vibrated along its longitudinal axis within the irrigating sleeve by the crystal-driven ultrasonic horn, thereby emulsifying the selected tissue in situ. The hollow bore of the cutting tip communicates with the bore in the horn that in turn communicates with the aspiration line from the handpiece to the console. A reduced pressure or vacuum source in the console draws or aspirates the emulsified tissue from the eye through the open end of the cutting tip, the cutting tip and horn bores and the aspiration line and into a collection device. The aspiration of emulsified tissue is aided by a saline flushing solution or irrigant that is injected into the surgical site through the small annular gap between the inside surface of the irrigating sleeve and the cutting tip.
One phacoemulsification tip that has gained widespread acceptance has a belled or flared distal end. Such a tip is described in U.S. Pat. No. 4,816,018 (Parisi). Such a design allows for larger lens material purchase as well as increased holding force when vacuum is applied to the tip while maintaining a smaller bore in the shaft of the tip. This combination of features increases anterior chamber stability, by reducing sudden outflow from the anterior chamber when the distal end becomes occluded and this occlusion breaks.
Another phacoemulsification tip is an angled or “bent” tip with or without a flared distal end. These tips are described in U.S. Pat. No. 6,039,715 (Mackool), U.S. Pat. No. 5,653,724 (Imonti) and U.S. Pat. No. 5,154,694 (Kelman). These tips have a predominantly straight shaft with the far distal portion of the shaft being bent on an angle. Bent tips are used by a great many surgeons, and are particularly useful when used in conjunction with a oscillatory phacoemulsification handpiece, such as those described in U.S. Pat. No. 6,352,519 (Anis, et al.) and U.S. Pat. No. 6,602,193 (Chon) and commercially available as the NeoSoniX® handpiece from Alcon Laboratories, Inc., Fort Worth, Tex., however; some surgeons are reluctant they feel that due to the proximal location of the bend it is more difficult to judge the position of the proximal cutting edge based on the extrapolation of the sleeved portion of the tip.
The inventors have discovered that swaged phacoemulsification tips are particularly advantageous when used in combination with torsional ultrasound handpiece. Torsional ultrasound handpieces are more fully disclosed in U.S. Pat. No. 6,077,285 (Boukhny). Therefore, a need continues to exist for a swaged phacoemulsification tip.